When I was first asked to write this column, among the editor’s requests were that I serve as “a guide through the climate crisis”. To do so, I tend to look for solutions, be they nature-based or policy, seek out experts or dig through scientific reports. But sometimes you only need to look out the window to understand what is happening.
The wettest 18-month period in England since Met Office records began in 1836 was from October 2022 to March 2024, with 1,695.9mm of rain. Soon after, September 2024 was the wettest in Oxfordshire (where I live) dating back to 1836, and in November Storm Bert brought 150mm of rain in just two days. Then came a spring, ongoing as I write, with no rain: the sunniest ever March, more wildfires raging by end of April than in any year since records began, in 2012, and the lowest rainfall in over a century come May.
On the other side of the world in Australia, and at first glance unconnected, more than four months’ worth of rain (over 400mm) have just fallen in two days in New South Wales, a volume widely reported as “unprecedented”.
But as records tumble around the world, none of this should be “unexpected”, while precedents aren’t hard to find. The last time New South Wales was hit by “unprecedented” and “once-in-100-year” 400mm of rainfall, for example, was only in 2021.
The obvious answer to “why” this is happening is “climate change”. But the cause of this lurching from flood to drought and back again is a hugely important climate statistic that most people have never heard of: for every 1°C rise in global temperature, the water vapour held in the atmosphere increases by 7 per cent. This isn’t mere prediction, but physics; the laws of thermodynamics playing out on a watery planet. Nasa analysis finds that Earth was 1.47°C warmer in 2024 than the late 19th-century preindustrial average. That means roughly 10 per cent more moisture in the atmosphere now compared to then.
This increased water vapour in the air means two things: more evaporation from the seas and soils, leading to more intense droughts and dry spells; and more intense rainfall (the atmosphere has more fuel—water vapour—to power rainstorms). This is now the pattern globally, entirely in-keeping with long-term climate change predictions.
The IPCC’s Impacts Assessment report published in 1990 warned of “precipitation in a warmer world” being “received in more intense storms” and “higher rates of evaporation”. Now, 35 years on, we are living it.
The English and Australian weather of the past few weeks are just two such examples. As Climate Council Australia have explained (to a press whose brief interest rises with flood waters and just as quickly recedes) the total amount of water vapour in the atmosphere reached a record value in 2024, at about 5 per cent above the 1991 to 2020 average. Broken down for Australia, this has meant 7 per cent to 28 per cent more rain during shorter rainfall (the type associated with flash flooding) and 2 per cent to 15 per cent more rain during longer rainfall: “This range is much higher than the 5 per cent figures that are used… by the likes of policy makers, engineers and urban planners.”
Once-in-a-century floods and droughts now appear seemingly every year. That they are still called “extreme weather events” is a misnomer. We are now living permanently on the “extreme” end of a spectrum never experienced by our grandparents or great-grandparents. Consider the UK breaking 40°C for the first time in 2022. Or the Valencia floods of last October and November. Or New South Wales in 2021 and 2025.
Five years ago, two academics from the UK’s Climate Change Committee (CCC) wrote, following that year’s flurry of “once-in-a-century” weather, of “an increase in the frequency, intensity, and/or amount of heavy precipitation”, and again pointed to the 7 per cent more moisture per degree of global warming figure—a stat I always look out for because, like the sun breaking through a gap in the clouds, it offers us brief and brilliant clarity.
There have always been terrible storms. But we know with some certainty that had those same storms formed and hit land a century ago, they would have brought less rain. Due to the 1.5°C of warming since, they had roughly 10 per cent more fuel (water vapour) to draw from. And, more often, they hit drier, parched soils, due to the increased evaporation in between.
Water vapour is also a greenhouse gas. As Nasa explains (in webpages not yet removed by the Trump administration), “because water vapor does not condense and precipitate out of the atmosphere as easily at higher temperatures… [it] then absorbs heat radiated from Earth and prevents it from escaping out to space. This further warms the atmosphere.” It’s estimated that this effect more than doubles the warming that would happen due to increasing carbon dioxide alone.
Perhaps I should end such an article with an upbeat “call-to-action”. The obvious one being that it’s not too late to curb carbon emissions, stop burning fossil fuels, etc, etc. But you already know that. I already know that. The authors of the IPCC Impacts Assessment in 1990 already knew that, as did the 19th-century scientists Nils Ekholm and Svante Arrhenius who first linked CO2 and the burning of coal to planetary temperature rise.
We must emit less. We must stop burning stuff. We are doing this, but far too slowly. More such “mitigation” is indeed the cure. But to treat the symptoms that we see out of the window, we need adaptation. The world will keep lurching between flood and drought. The new reality is that we must learn to adapt and survive.
